When a desktop or a notebook computer's hardware resources are shared by several nonconcurrent users, conventional wisdom finds that a secondary user's inadvertent corruption of a primary user's files and programs is a potentially troublesome problem. Such data corruption may occur due to simple operating error, malicious intent, accidental modification caused by installation of new and sometimes inherently faulty software, and usage of aggressive code-level utility programs such as Norton's Utilities which may unwittingly act to erroneously modify bytes of binary code just about anywhere in a file or on a hard disk.
A more subtle problem is an introduction of a software virus into a mutually shared boot sector or operating system, particularly when the virus is (albeit inadvertently) introduced by one user, unbeknownst to the other user. While no computer virus can physically destroy (e.g., literally destroy) a hard drive, the data can be erased or irreparably damaged by the virus. This includes possible corruption of the boot sector of the hard disk drive. With about 7,500 known viruses travelling around in the software world (with about 1,400 discovered in 1995 alone!) it behooves the prudent user to concern himself with realistic protection if he considers his data and program files vital to his business wellbeing.
The ultimate result is a catastrophic failure of the primary user's software operability, file data corruption, or loss and failure of file retrieval functions. Conversely, the primary user may similarly corrupt operational integrity of the secondary user's files or programs.
One user may also unintentionally alter the operating characteristics of another user's applications through modifications to shared shell software components including SYSTEM.INI, WIN.INI, SYSTEM.DAT, USER.DAT, various .POL files, or similar initialization and setup files. Such unintentional cross-file corruption most commonly occurs due to routine installation of new software or changes in operational setup of existing application software. Under a Windows operating shell (i.e., Microsoft Windows 3.11 or Windows 95) the WIN.INI and other .INI and .DAT files are especially vulnerable when different applications programs are installed. In particular, action games can cause havoc with the WIN.INI (and similar .INI) personality file settings in order to optimize game operation at the sacrifice of other office application programs, such as word processors and the like. The result of such unpredictable file corruption may, at the very least, manifest itself as unexpected operation of earlier-installed applications programs.